Examples/lwip: sntp example - Make SNTP server configurable

Also updates NTP example test to allow more attempts

examples/protocols/sntp/example_test.py

@@ -15,7 +15,7 @@ def test_examples_sntp(env, extra_data):
 
     dut.expect_all('Time is not set yet. Connecting to WiFi and getting time over NTP.',
                    'Initializing SNTP',
-                   'Waiting for system time to be set... (1/10)',
+                   re.compile(r'Waiting for system time to be set... \(\d+/\d+\)'),
                    'Notification of a time synchronization event',
                    timeout=60)
 

examples/protocols/sntp/main/Kconfig.projbuild

@@ -1,5 +1,11 @@
 menu "Example Configuration"
 
+    config SNTP_TIME_SERVER
+        string "SNTP server name"
+        default "pool.ntp.org"
+        help
+            Hostname of the main SNTP server.
+
     choice SNTP_TIME_SYNC_METHOD
         prompt "Time synchronization method"
         default SNTP_TIME_SYNC_METHOD_IMMED

examples/protocols/sntp/main/sntp_example_main.c

@@ -183,8 +183,8 @@ static void initialize_sntp(void)
 #endif  /* LWIP_IPV6 */
 
 #else   /* LWIP_DHCP_GET_NTP_SRV && (SNTP_MAX_SERVERS > 1) */
-    // otherwise use DNS address from a pool
-    sntp_setservername(0, "pool.ntp.org");
+    // otherwise, use DNS address from a pool
+    sntp_setservername(0, CONFIG_SNTP_TIME_SERVER);
 #endif
 
     sntp_set_time_sync_notification_cb(time_sync_notification_cb);